Golf ball having reduced side spin

ABSTRACT

A golf ball has one or more grooves in the ball surface. When the ball is initially struck by a golf club at an oblique angle the ball can have an undesired side spin. Each groove in the ball surface interacts with the air stream to absorb some of the side spin energy. The grooves act like miniature turbine blades, or vanes on an in-flight arrow, to decelerate side spin velocity so as to reduce the tendency of the ball to hook or slice.

CROSS REFERENCE TO A RELATED PATENT APPLICATION

This is a continuation-in-part of my co-pending U.S. patent applicationSer. No. 11/975,556 filed on Oct. 22, 2007. Any patent issued hereonwill date from Oct. 22, 2007, i.e. the filing date of the co-pendingpatent application.

FIELD OF INVENTION

This invention relates to golf balls and particularly to golf ballhaving reduced side spin. Side spin is a spin generated around the golfball center in a plane oblique to the flight path of the ball. Side spinis produced when the face of the golf club strikes the ball at anoblique angle to the path of the club. The present invention relates toa golf ball that is constructed to oppose side spin forces generated bythe oblique angle striking force of the club face.

DESCRIPTION OF THE RELATED ART

Side spin of a golf ball is undesired because it causes the ball to takea curved path after it leaves the club face, so that the ball goes offcourse from the direction intended by the golfer. With a right-handedgolfer a curvature to the right is termed a slice, and a curvature tothe left is termed a hook.

U.S. Pat. No. 7,041,011 issued to M. J. Sullivan et al on May 9, 2006discloses a golf ball designed to have a relatively low spin rate, withan associated lowered tendency to hook or slice. The golf ball has anouter layer containing regions of weighting material that providesperimeter weighting for the ball. Such perimeter weighting increases themoment of inertia of the ball, which the patentees believe causes theball to have a lower spin rate, compared to a conventional golf ball.

SUMMARY OF THE INVENTION

The present invention relates to a golf ball having one or more groovesin its spherical outer surface. Each groove has a sufficient width anddepth dimension so that when the ball is airborne a ball-related laminarair flow is achieved in each groove, thereby generating resistance toside spin of the ball. Each groove acts as a miniature air vane that hasa turbine-like resistance to the side spin force. The turbine-likeresistance exerts a braking action to reduce the side spin and minimizethe ball slice or hook (depending on the direction of the side spin).

The action of the groove in the golf ball surface is somewhat similar tothe action of the fletches or vanes on an in-flight arrow. In each casethe vane reacts to a disturbing force to stabilize the in-flight object(golf ball or arrow). In the case of the arrow the vane reacts to thedisturbing force to produce stabilizing spinning motion of the arrowaround the arrow axis. In the case of the golf ball the vane (groove)reacts to the side spin force so as to absorb the side spin energy,thereby reducing the undesired side spin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a conventional golf ball in flight afterbeing struck by a golf club.

FIG. 2 is an enlarged fragmentary sectional view of the FIG. 1 golfball, showing certain turbulence-producing dimples on the golf ballsurface.

FIG. 3 is a plan view of a golf ball embodying the present invention.FIG. 3 includes two lines showing the air separating and then flowingaround the ball surface as the ball moves in a left to right direction.

FIG. 4 is a sectional view taken on line 4-4 in FIG. 3.

FIG. 5 is a fragmentary enlarged sectional view of the FIG. 3 golf ball,showing in cross section a groove in the ball spherical surface. Whilethe ball is in flight in the groove accommodates a laminar air flow thatprovides a resistance to side spin of the golf ball.

FIG. 6 is a fragmentary sectional view taken on line 6-6 in FIG. 5.

FIG. 7 shows the FIG. 3 golf ball while in-flight prior to alignment ofan air flow groove with the main air stream flowing over the ball.

FIG. 8 shows the FIG. 7 golf ball after the air flow groove has beenaligned with the air stream generated by the golf ball.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is shown a conventional golf ball 10 afterbeing struck by a golf club, so that the ball is moving in a left toright direction in an ascending path, designated by numeral 12. The ballis shown in cross section to illustrate the ball internal structure. Theball includes an inner spherical core 12 having a center 16, and anouter cover 18 molded onto the core. The outer spherical surface 20 ofthe cover is covered with small dimples 21.

The ball can have a diameter of 1.68 inches, as required by the U.S.Golf Association. Each dimple 21 can typically be a circular depressionhaving a diameter 23 of about 0.13 inch and a depth 25 of about 0.010inch. Cover 18 may have a thickness on the order of 0.1 inch. The ballinteracts with the stagnant air in the path of the ball to form an airseparation point 22 in front of the ball, an air attachment zone 24downstream from air separation point 22, and a turbulent wake area Wdownstream from air attachment zone 24.

The function of dimples 21 is to promote attachment of the air to thespherical surface of ball 10 so as to lengthen air attachment zone 24(along path line 12).

In air attachment zone 24 dimples 21 generate localized boundary layerturbulence that interacts with the relative laminar flow of air spacedfrom the ball spherical surface 20, such that the laminar flow isattached to the ball surface.

The term “relative laminar air flow” is used herein to mean a flowrelative to ball 10. In actual terms the air is relatively stagnant inthe directions of ball movement; however the air is considered to moverelative to the ball.

The present invention relates to a modification of the conventional golfball (FIG. 1) that reduces the side spin of the ball that contributes toball slice or ball hook (i.e. undesired curvature of the ball from astraight trajectory). As illustrated in FIG. 1, side spin can be aspinning motion of the ball around the ball center 16 (or a point nearthe center) in a direction generally transverse to the ball flight path,as indicated by arrow 26. Side spin is believed to be caused when theface of the club head strikes the ball at an oblique (non-normal) angleto the path of the club head. The present invention provides one or moreelongated grooves in the ball surface that interact with air in airattachment zone 24 so as to resist the side spin force generated whenthe club head strikes the ball obliquely.

FIGS. 3 and 4 show a golf ball embodying the invention. The illustratedball has three elongated grooves 28 spaced equidistantly around the ballcircumference, as shown best in FIG. 4. When the ball is airborne thethree grooves interact with the air surrounding the ball so as to bealigned with the stream of air attached to the ball spherical surface.The term “aligned” is herein used to mean generally that each grooveextends parallel to the air stream, such that laminar flow velocity airin air attachment zone 24 can move through each groove while remaininggenerally parallel to the ball flight path 12. Each groove has acircumferential component (as indicated by the curved dashed lines inFIG. 3) so that laminar air flowing through each groove remainscontiguous with and attached to the main air stream surrounding theball. The “air flow” mentioned herein is flow relative to the movingball, not flow in the absolute sense.

One of the side surfaces of each groove 28 functions as a miniatureturbine blade (or arrow vane) to oppose the side spin forces designatedby arrow 26. Each groove 28 absorbs some of the side spin force so thatduring the course of ball travel the side spin rate decreasesappreciably, thereby eliminating or reducing the undesired slicing orhooking action. In this context, a slice is associated with side spin inone direction, whereas a hook is associated with side spin in theopposite direction. Grooves 28 resist side spin in either direction. Thegrooves act cumulatively.

As the air in the air attachment zone 24 enters each groove 28 it haszero velocity in the arrow 26 direction. Spinning movement of the golfball in the arrow 26 direction causes one side wall of each groove 28 toaccelerate the air in the arrow 26 direction from a zero velocitycondition up to the side spins velocity of the golf ball. Theacceleration energy is absorbed by the golf ball so that eventually theside spins is eliminated or substantially reduced, as noted above.

When the ball is struck by the club head, grooves 28 can have a randomorientation (not necessarily aligned with the ball flight path or airmovement direction). During the initial stage of the ball travel grooves28 interact with the air in air attachment zone 24 to turn the ball to aposition where the grooves are aligned with the air stream in zone 24.Again, “air stream” means flow relative to the moving golf ball.

FIGS. 7 and 8 illustrate generally how the ball can be turned to aligngrooves 28 with the air stream in air attachment zone 24. In FIG. 7,groove 28 is at some random angle to flight path 12 and the associatedreversely flowing air stream. Laminar air surrounding the ball flowsthrough groove 28, as shown by arrows 30. The flowing air interacts withside surfaces of each groove 28 to turn the ball into a position whereinthe grooves are aligned with the ball flight path (and direction oflaminar air flow). In the FIG. 8 ball position grooves 28 are enabled toresist undesired side spin of the ball, while offering minimalresistance to forward ball movement.

It will be seen from FIG. 3 that each groove 28 has a length that isapproximately the same as the length of air attachment zone 24. Thegrooves are long enough to interact with the laminar air flow in zone 24without being directly exposed to the turbulent air generated atseparation point 22 or the turbulent air in wake area W. Flow througheach groove 28 is essentially high rate non-turbulent laminar flow,which is preferable for absorption of side spin energy. Each groove hasa length that is a major portion of the distance between imaginarypoints 32 and 33, measured along the ball surface (i.e. more than fiftypercent of the distance between points 32 and 33).

Grooves 28 are of similar length, as shown in FIG. 3. The groovesterminate at a common distance from two imaginary points 32 and 33located on a diametrical line 35 passing through golf ball center 16.The grooves interact with air in air attachment zone 24 to oppose sidespin rotation of the ball, without introducing any significant adversedisturbing force onto the ball.

Each groove 28 has sufficient depth and width to accommodate a desiredvolume of laminar velocity air in zone 24. FIG. 5 shows one crosssection that each groove can have. Preferrably the groove depth is onthe order of about 0.05 inch. Similarly, the groove width is about 0.05inch. Typically, the golf ball cover 18 has a thickness of about 0.1inch. Each dimple 21 has a diameter 23 of about 0.13 inch, and a depthdimension 25 measuring about 0.01 inch, which is conventional in golfball construction practice.

The width and depth dimensions for each groove 28 are several times thedepth dimension of each dimple, whereby the groove has sufficient crosssectional area to accommodate laminar air flow. The turbulent boundarylayer on the groove side walls and groove bottom wall is insufficient tochoke off laminar air flow through the groove. As noted above, FIG. 5shows groove 28 having a depth of about 0.05 inch and a width of about0.05 inch. The depth of each associated dimple is about 0.01 inch. Withsuch dimensions the groove depth (or width) is about five times thedimple depth. In preferred practice of the invention the groove depth(and width) is at least five times the dimple depth so that air in eachgroove has a laminar flow relative to the ball.

Dimples 21 are not shown in FIGS. 3 and 4. However, it will beappreciated that, in practice, the non-grooved area of the golf ballspherical surface can be covered turbulence-generating dimples. Thepresent invention is concerned particularly with the provision of one ormore air interaction grooves 28 in the golf ball spherical surface. Thegolf ball can be dimpled per conventional practice.

End areas of each groove merge gradually with the spherical surface ofthe golf ball, as shown in FIG. 6. The bottom wall of each groove has aramp like continuation 37 that merges with surface 20 of the ball at arelatively small angle. The aim is to minimize turbulence that mightinterfere with a smooth flow of air into or out of each groove 28.

1. A golf ball having a center and an outer spherical surface concentricaround said center so that when the ball is airborne the air in the pathof the ball interacts with the ball to form an air separation point infront of the ball, an air attachment zone downstream from the airseparation point, and a turbulent wake area downstream from the airattachment zone; multiple elongated grooves in said spherical surfaceadapted to interact with air in the attachment zone so as to be alignedwith the stream of air attached to the ball spherical surface; each saidgroove having a depth dimension and a width dimension causing theball-attached air in said groove to have a laminar flow velocityrelative to the ball, whereby each said groove generates a resistance toside spin of the golf ball; each said groove extending along the ballsurface between two imaginary points located on a diametrical linepassing through the golf ball center, each groove having a length thatis a major portion of the distance between the two imaginary points,whereby each said groove is in contact with essentially the entirelength dimension of the air attachment zone; the non-grooved areas ofsaid spherical surface being covered with turbulence-generating dimples;each dimple having a depth dimension; the groove depth dimension andwidth dimension each being at least five times the dimple dimension sothat air in each groove has a laminar flow relative to the ball.